Who decided the Body Descriptions? What is overweight?

by Steven B.Halls, MD FRCPC

A Body Mass Index between 25 and 29.9 is "overweight", and greater than or equal to 30 is "obese", according to an old definition1. This definition is used by the World Health Organization (WHO) as its international standard3. You can read more about it, (including its problems).

I’ve heard of that. BMI of 25 is called overweight.

The oldest version of the halls.md body mass index calculator used an even older definition of Overweight. It was based2,8,11 on this table below (for adults). You can still use this table if you like. Simply calculate your BMI, then refer back to this table.

Adults

Women

Men

anorexia

< 17.5

underweight

<19.1

<20.7

in normal range

19.1-25.8

20.7-26.4

marginally overweight

25.8-27.3

26.4-27.8

overweight

27.3-32.3

27.8-31.1

very overweight or obese

>32.3

>31.1

severely obese

35 – 40

morbidly obese

40 – 50

super obese

50 – 60

I don’t like that table of numbers.

I didn’t bother reading it.

For children, there was no suitable BMI criteria (until around year 2000), which was a weakness of previous versions of the BMI calculator. (Actually, nearly all other BMI calculators on the internet are still not suitable for use for children.) See below for recent changes!

For older adults, the previous halls.md calculator was using an age adjustment, by adding 1 extra BMI unit per decade of age, starting at age 45, to the criteria shown in the table above7.

The Old old halls.md BMI calculator in 1999. Then in year 2000 it became much better, and in year 2014 I have updated the styling, and found new research.

New Features, New BMI criteria:

A year 2000 addition to the halls.md body mass index calculator, was a proper method to judge Children’s BMI according to Age, using the CDC criteria. That was a significant improvement and its a unique feature amongst on-line calculators. The thresholds for Adults BMI were set to use the CDC criteria as the default method.

And in year 2014 I changed the default criteria to be “halls.md v2″ which by then had extensive research literature support.

You were ahead. It took years for mainstream to catch up.

Here is my discussion of how the ‘halls.md v2′ method for judging Adults BMI according to age was developed. It’s interesting, and contains some good science.

Even so, there are still some problems using BMI to determine overweight. Some very muscular people can have high Body Mass Indexes, which wrongly suggest fatness. Some races, ethnic groups and nationalities have different body fat distribution and body composition, so different BMI criteria are needed. I hope to improve the calculator in these areas, in the future.

Weight and Height percentiles

Unlike the Body Mass Index formula, the formula for height and weight percentiles is an estimate, rather than an exact calculation. But it’s a GOOD thing. A percentile is not the same as a percent. Your percentile rank indicates how your measurement compares to the recent American population. For example, an adult whose weight is at the 50th percentile, is very close to the average weight of the population. An adult at the 90th percentile is quite heavy, and 90% of the population would be lighter.

According to the CDCover half of American adults are overweight (55%)? Apparently so, according to the the NHANES surveys. It is possible to be labelled as overweight, even if your weight is below the 50th percentile. This bothered me, and maybe you too? So I developed my own criteria: the halls.md v2 criteria. (And update in 2015, many years later, I’m thinking of making a version 3 criteria, based on newer information.)

A little history of this website. The oldest version of my calculator was calculating percentiles based on older data. It was like comparing yourself to an "idealized" population from about 35 years ago. Now, the current halls.md calculators are using the most recent data available, from a fatter recent American population. It’s not flattering to Americans in general, but at least there is more room for you, in middle ranges of percentiles.